you be able to tell if theres a problem with the PH untill you get a meter or you see the leaves turning yellow or witling etc, you say it says the ph is 5.0 ? 5.0 should be fine for now , eventually you will probably need to add Magnesium and Nitrogen to the mix , atleast this is the prob i got , I needed to add Magnesium , if your leafs start to yellow , look online at the problem chart with plants , just google , "nutrient diffiencies marijuana" and you should find a chart describing the symptoms with pics , then adjust from there , if you do get magnesium diffiency just buy epsom salts at your local CVS , Wallmart , etc and mix in a TBSP per gallon of water .. How many CFL's do you have ?